Rock-drill bit.



'c.}-A'. BRAW-N'l ROCK DRILL BIT.

APPLICATION FILED MAR. 23. 1918.

1 2,83,-646.. Patented Nov. 5, 1918.- 3 SHEETS-SHEET 1.

Vi I I 175W??? l waxes, v I I v I J dfa 4 w 57m C. A. BRAWN.

00K DRILL an. APP AT ON FILED MAR-23, 191B.

1,283,646. lutentvd Nov. 5,1918. 7 3 SHEETS-SHEET 2.

C. A. BRAWN.

aocKumL'L an. AP?LICATION FILED MAR. 2 3. I918 I 1,283,646; Patented Nov. 5,1918.

3 SHEETS-SHEET 3.

aocK-nRILn BIT.

Division in part of application Serial No. 224,149, filed March 23 i r 1918. Serial No. 224,150.

To all .wizomz't may concern: I

Be it known that I, CHARLES A. BRAwN, a citizen of the United'States, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, tain new and useful Improvements in Rock- Drill Bits, of which the following is a specification.

The main object of my present invention, as in' my other application for United Statespatent for. rock drill bits, filed March 23, 1918, Serial No. 224,149, is-to construct such drill bits in a manner that all portions of the cutting edge on the active surface thereof will perform substantially the same ainountof work thereby reventing one cutting portion of the bit rom-wearing away sooner than other cutting portions ofthe bit as 'has been the difficulty with drill bits made and used prior to myinvention; it being known that when one portion of the cutting edge, circumference, wears more quickl than another portion, the drill bit oftenbecomes bound' within the drill hole of the rock or the. like and must be removed and a bit of smaller diameter inserted to drilling operation.

.The mechanical principle on which my improved drillbit is, based and constructed is the distribution of cutting edge on the continue the active face of the drill bit in'prop'orti'on to the area over which the respective portions ofsaid face of the drill will operate in one of the drill; the princicomplete revolution being especially appliple of construction cable to drills which operate by successive blows against the surface to be drilled with a rotary motion of thedrill between each blow. This principle'is carried out 1n structure by providing a drill bit in which the cutting edge is recessed or interrupted at points on the face of the bit where otherwise the edge be in proportion to the area covered by the drill in its operatiton.

The mathematical principle involved in making the proper distribution'of cutting edges, as above noted, is the ratio of. the areas of concentric annuli' into which the surface to be drilled may be considered to be divided. Since the area of an annulus equals the sum of its diameters divided by the difference of its diameters'and this quo- Specification of Letters Patent. v

have invented cerwhich will be withinits length would not- Patented Nov. 5, 1918. 1918.' This application filed March 23,

tient multiplied by the constant .7854, it

follows that if around a central circle there are to be several cumscribed circle,

successive annuli, width equal to the radius drawn, or considered to be drawn,

.each of a radlal of the central cirthen the area of such ana null may be expressed as multiples of the area of the central circumscribed circle and in relatlon, to each other. in the constant ratio 1 of 1, 3, 5, 7,

equals the area of the central 9, etc., in which one circle and the otherfigures the relative areas of the successive annuli from the center outward.

For the sake -0f simplicity and to permit the ready comprehen sion of this principle of the ratio of the areas of concentric annuli of equal radial width, and also some unequal radial width, I have included various diagrammatic illustrations in the accompanying drawings to show the application of the distribution of the cutting edges by exhibiting widths, but it will be exact calculations would reduce annuli of convenient understood that more I the width and increase the number of annuli finally to v a polnt beyond the p This obj ect in the following ma ossibility of mechanical application and toward infinity.

' and other advantageous ends described hereinafter, I attain nner, reference being bad to 'thefaccompanying drawings in which Figure I is a perspective view of a drill bit embodying the principle of my present invention and 'includi portions,

Fig. 2 1s a top plan inFig. 1,

*Fig. 3 is a side elev in Figs. '1 and 2,

ng three cutting edge view of the bit shown ation of the bit shown Fig. 4 is a perspective view of a. bit constructed 1n accordance Wltll my invention and lncludln'g four cutting edge'portions,

Flg. 5 is a top plan in Fig. 4,

view of'the bit'shown Fig; 6 is a side elevation looking in the direction of the arrow a,

of Fig. 5,

F 1g. 7 is a side elevation of the bit looking in the direction of the arrow 6, of Fig. 5

F g. 8 is a section taken on the line 88 of Fig. 5, Fig. '9 is a perspective view of a drill bit made in accordance-with my invention and including seven cutti ng edge portions and includes a circle D and annuli E and F.

The annulus F has an area of 1228-11 square inches to be cut by 21 g of cutting edge, the latter being provided in equal parts of each by the portions 13, 14, and 15. This represents a proportion of 5.0396 square inches of surface per one inch of cutting edge. The annulus E has an area of 9.4248 square inches to be cut by 2 of cutting edge, said 2" being provided in equal lengths by the remaining parts of the cutting edge. portions 14 and 15. This represents a proportion of 4.7121 square inches per one inch of cutting edge. The circle D has an area of 3.146 square inches and is cut solely by 1 of cutting edge supplied by the cutting edge portion 12.

In the form of my invention illustrated in Figs. 9, 10, 11, and.12, I have shown a bit in which the cutting end surface 22 is formed by slx wings 23, 21, 25, 26, 27, and The cutting edge is divided into seven portions29, 30, 31, 32, 33, 3-1, and 35. The cutting edge portion 29 extends from the axis toward the circumferential surface 36 of\ the wing and the interruption between this portion 29 and the portion 30 is produced by a recess 37, the portion 30 extending from the recess to said circumferential surface 36. The interruption between the cutting edge portion 29 and the cutting edge portion 33 is made bya recess 38. said recess interrupting or stopping the portion 29 at the axis. The remaining cutting edge portions 31, 32, 34, and V mote from the axis and extend to the respective circumferential surfaces of the wings 24, 25, 27, and 28 with which they are in direct alinement. The gaps. or interruptions between the cutting edge portions 31, 32, 34, and 35 are made by providing recesses 39, 40, 41, and 42.

Fig. 15 is a diagrammatic representation of the work capable of being performed by the bit illustrated in Figs. 9 to 11, inclusive, and in said Fig. 15 is illustrated a circle J and annuli K and L. Considering that the bit isto drill a hole 3 in diameter and includes 5} ofcutting edge, the following result will be obtained: The annulus L has an area of 3.9270 square inches to be cut by 3 of cutting edge supplied in equal lengths by the cutting edge portions 30, 31, 32, 33, 31, and This represents a proportion of 1.3090 square inches per one inch of cutting edge. The area of the annulus K is 2.3562 square inches to be cut by 1% of cutting edge of which the portion 33 supplies 1} and each of the portions 31, 32, 34, and 35 supplies of 1.34% square inches per one inch of cutting edge. The circle J has an area of .7854 square inch to be cut by -1= of cutting edge.

. This is supplied solely by the portion 29 and represents a proportion of 1.5708 square 35 begin at points re- This represents a proportion inches per one inch of cutting edge. It will thus be noted that all portions of the cutting edge in the form of my invention illustrated in Figs. 9 to12, inclusive, perform practically the same amount of work and by the provision of the recesses inthe location as specified, I am enabled to secure a bit in .which all the cutting surfaces are practically balanced and in which the wear will be substantially equal on all portions of'the cutting edge.

I wish it understood that while I'have shown a number of different formsof bits and cutting edges my invention includes any bit having cavities, recessed surfaces, or interruptions in the cutting edges so as to distribute the active cutting edges on the face of the bit in proportion to the area of the surface over which they will operate in one complete revolution of the bitand in which certain of these interruptions of the cutting edge adjacent to the centralpart of--., the blt start from the axis of the bit and others being located at positions remote from the axis and not touching the same. My invention, therefore, includes any bit having a portion providing a cutting edge which is interrupted in its length by a recess in which a point on theperimeter of the recess or in terruption to the cutting edge coincides with the axis of the bit and in which the cutting edge has other interruption provided by a recess in which no point on said latter recess coincides with or touches the axis of the bit.

lVhile I have described my invention as taking a particular form, it will be under-' stood that the various parts of my invention may be changed without departing from the spirit thereof, and hence I do not limit myself to the precise construction set forth, but consider that I am at liberty to make such changes and alterations as fairly come within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secureby Letters Patent is:

1. A drill bit including a surface providing a cutting edge the length of which is included in a'plane at right angles to theaxis of the bit and in which the cutting edge is interrupted by a recess, the point of inter ruption of the cutting edge by the recess beginning at the axis of the bit, said outting edge being interrupted by another re- 

